New insights into the deactivation mechanism of V₂O₅-WO₃/TiO₂ catalyst during selective catalytic reduction of NO with NH₃: Synergies between arsenic and potassium species

Synergies between arsenic (As) and potassium (K) species in the deactivation of V₂O₅-WO₃/TiO₂ catalyst were investigated. Both arsenic oxide and potassium species presented a serious poisoning impact on catalyst activities, and the extent of poisoning of (As + K) was much stronger than their single superposition. The intrinsic reasons were explored and analyzed by N₂ physisorption, XPS, H₂-TPR, NH₃-TPD, NH₃-DRIFTS and in situ FTIR. Results indicated that BET surface area decreased due to the formation of a dense arsenic coating on the catalyst surface. V-OH active sites were destroyed by arsenic and As-OH acid sites were newly generated. After potassium species were added to arsenic-poisoned catalyst, K⁺ further neutralized the As-OH acid sites, and the amount and stability of both Lewis and BrØnsted acid sites decreased more greatly. Potassium also reacted with intermediate NH₂^- when the temperature was elevated to higher than 250 °C, which resulted in more NH₃ consumption and NH₃-SCR reaction inhibition. The extent of deactivation was related to the potassium species when both poisons reacted on the catalyst, and the influence sequence followed AsKS < AsKN < AsKC. As₂O₃ + K₂SO₄ presented the weakest impact among these three poisoned catalysts due to the resistance of SO₄^2- to arsenic.